Engine ignition systems may include a spark plug for delivering an electric current to a combustion chamber of a spark-ignited engine, such as a gasoline engine, to ignite an air-fuel mixture and initiate combustion. Spark plug fouling may occur wherein a firing tip of the spark plug insulator becomes coated with a foreign substance, such as fuel or soot. Soot-fouled spark plugs include a carbon build-up on an electrode of the spark plug, whereas wet-fouled spark plugs include liquid fuel build-up around the electrode. Spark plugs may become wet-fouled due to engine flooding, for example. The engine may flood due to rich fueling during extreme temperature weather conditions, when an operator depresses/pumps the gas pedal repeatedly during cranking, or due to excess fuel inside the cylinders (e.g., due to a degraded fuel injector). When the spark plugs become wet-fouled, they are unable to produce a spark across the electrode, thus delaying or preventing engine start. Engine flooding may also affect other in-cylinder components and delay engine start when the cylinder includes other forms of ignition. In some instances, engine flooding may cause a frustrated vehicle operator to continue cranking the engine until the battery drains. Further, vehicle emissions may be increased due to repeated unsuccessful cranks while the engine is flooded.
Common services remedies to address engine flooding include removing the spark plugs and drying them with compressed shop air or a heat gun. Still other remedies include leaving the engine to sit for a while to allow the fuel inside the cylinders to vaporize. However, such approaches are intrusive and/or time consuming. In addition, vehicle operators may not be able to start the engine when requested.
Other attempts to address spark plug wet-fouling in a less intrusive manner include methods for removing fuel adhered to the spark plug while the spark plug remains in the engine. One example approach is shown by Ayame et al. in U.S. Pat. No. 7,523,744 B2. Therein, a method is disclosed that cranks the engine without injecting additional fuel in response to an indication that the engine has not started properly (e.g., within a duration of beginning the cranking).
However, the inventor herein has recognized potential issues with such systems. As one example, cranking the engine without providing additional airflow to dry the spark plugs (or other flooded cylinder components) may be inefficient, resulting in increased engine starting times. The increased engine starting times may increase vehicle operator frustration as well as drain the battery. In addition, tailpipe emissions may be increased with repeated and unsuccessful cranking of the flooded engine. Still other approaches may rely on an electric booster to blow air into engine cylinders while spinning the engine unfueled to dry the spark plugs. However, such approaches may be limited to vehicle systems configured with an electric booster.
In one example, the issues described above may be addressed by a method comprising: in response to flooding of an engine with fuel during an engine start attempt, shutting off fuel delivery to an engine cylinder and operating a laser ignition device to vaporize the fuel while holding an exhaust valve of the cylinder open and an intake valve of the cylinder closed. In this way, a flooded combustion chamber may be dried efficiently and non-intrusively.
As one example, an engine system may be configured with laser ignition. If a controller determines engine flooding has occurred during an engine start (such as responsive to a lack of engine start following cranking, and/or based on rich UEGO sensor output during the start), a drying routine may be initiated. Therein, the engine may be spun, unfueled via a motor, to park a first engine cylinder at a position where an intake valve is closed and an exhaust valve is open (such as at a top of the exhaust stroke). Then, while the engine is held at that position, a laser igniter may be operated for a duration to vaporize liquid fuel in the cylinder. If the laser is maneuverable, a beam direction and focal point may be adjusted on different regions of the cylinder (e.g., at random or targeted) so as to vaporize fuel throughout the cylinder. Since the exhaust valve is open, the vaporized fuel is directed out of the cylinder and into the exhaust passage, resulting in a rapid and efficient drying of the given cylinder. The engine is then rotated by the motor to park a second engine cylinder at a position with the intake valve closed and the exhaust valve open, and laser operation is used to dry this cylinder. In the same way, all engine cylinders may be sequentially dried. Thereafter, an engine start may be reinitiated.
In this way, engine flooding may be addressed without requiring removal of cylinder components or additional hardware. By drying the engine using heat generated via a laser igniter coupled to the cylinder, engine starting times may be decreased and reproducibility of engine starts is improved. Further, battery consumption may be decreased. Overall, wet-fouled cylinder components may be dried faster. By improving the quality of engine starts, vehicle operator frustration is reduced.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.